New 12Z GFS has just finished running. The west coast ridge is a bit weaker on this mornings run. The Short Waves (Storms) for Tuesday/Wednesday and again early the following weekend are more progressive. This once again enhances the odds for snowfall in the high country next week. Will have a look at the 12Z ECMWF as soon as it finishes about 12:00 PM today. The 12z GEM as well.

Stay Tuned……

———————————–>>>>

This Mornings extended guidance continued the trend showing an amplified upper flow pattern at 18000ft from the central pacific to the east coast of the CONUS. The models are predicting trofs to remain over the Bering Sea/Aleutians and East/Central North America.

The pattern continues to be very amplified including the more dominant west coast ridge in between. This morning Global Forecast Model’s (GFS) deterministic run continued the trend of “Some” short wave energy undercutting the west coast upper ridge next week. However, the trend is certainly weaker with the mid week short wave. IE the Tuesday/Wednesday storm)

Looking at the 2 week ECMWF 5 day means hemispheric guidance, the planetary wave pattern transits to a three wave from the current four wave pattern. The Blocking high over NWT/AK is expected to retrograde to Siberia, while the trof over the Bering Sea is expected to progress eastward into the Eastern Central Pacific. The upper flow pattern over the eastern pacific should become more active during week 2 with the upper jet aimed more toward Northern CA and Oregon. The Pacific NW is thus likely to get another bout of heavy precipitation week 2. At the moment, 500MB 5 day means between the 22nd and the 27th of NOV for heights on the ECMWF 500mb Ensemble control are still about 570DM over Mammoth, which is border line for precipitation here in the central sierra, unless it taps a lot of subtropical moistures along the way. The Dweebs will follow the trend to see what changes there may be in the location of the upper jet the next couple of weeks.

In conclusion, fighting the west coast upper ridge….The models have been back peddling on the Tuesday/Wednesday system the past 2 days…. As it is not clear at this time on how it will hold together as it comes through the west coast ridge Tuesday night and Wednesday. If I had to take a wild guess at this point I would say any ware from a couple of inches to as much as 8 inches depending on again….how it holds together, or if it splits and goes south into Southern CA. With that said, the upper ridge will begin to weaken next week as the upper pattern goes into transition later in the week. If by chance the upper trof over the Bering sea decides to progress further east to say 130W to 140 west…..that would make a big difference in heights over the central west coast.

As a side note; even though a lot of the teleconnection’s and indices effecting what we might expect weather-wise across the US are different this year, the eastern pacific ridge is still the dominant feature effecting California’s weather and for that matter its ongoing drought. So far, the expected enhanced upper jet has yet to show up related to the developing El Nino. However, that is not unexpected, as it is still only mid November as the East Asian Upper Jet out over the Pacific is still quite incipient.

We will need the enhancement by El Nino to strengthen the upper subtropical Jet or the southern branch of the polar jet enough to plow through a persistent developing west coast ridge. Especially In light of a winter-like pattern already getting established over much of the CONUS. This pattern will tend to support a deep trof over the nations mid section and a Simi permanent ridge along the west coast. This was the classic pattern of 76-77.

What the Dweebs are seeing are several storm possibilities within the westerlies that are being weakened by the west coast ridge causing the systems to weaken and split. These systems lack cold air as well.

For the up coming week I see three systems:

1. A very weak system that pretty much falls apart Thursday bringing a chance of showers

2. A back door dry cold front giving us a sample of the colder air that is currently over and east of the Rockies late this weekend

3. Another system that will weaken next Tuesday, and yet another system a few days later. Each one of these systems are coming through the west coast ridge. The upper ridge does flatten next week. So amounts will probably be in the light to moderate range. As little as 6 inches and as much as 18 inches is my best guess. Again….This is just an educated guess at this point, based more on the pattern rather than the extended guidance. The Dweebs will have a much better handle on the system by the end of the weekend.

Being optimistic, I guess the best news is that is that if the ENSO signal continues to strengthen in the El Nino mode into December next month, a stronger upper jet is likely to cause a pattern change that will make it more difficult for the Polar Vortex to remain entrenched where it is likely to set up over the coming weeks….

The concept is this. A stronger upper subtropical jet comes into the west coast over Southern CA or Baja, and as it moves east through the southern states, it then swings northeast and flushes out the cold air from the CONUS…..out over the Atlantic, thereby opening up the wavelength…..

That is what the Dweebs are hoping to see later in this or next season……………………..

The rest of the pattern is common with El Nino, during the Fall and Winter with a blocking high over the NWT and AK and the westerlies suppressed underneath. .

The Dweeber……………………:-)

——————————————————————————————————————————————

Tuesday Night Update:

In looking at the latest guidance…there is still a lot of questions on how much short wave energy of the westerlies will hold together as it penetrates the upper west coast ridge over the next two weeks. In that the system’s will weaken…..The big question will be how much. On an exciting note, the latest Nino region update shows that between Nino regions 3 to 4, all the SST anomaly’s are now at least +.8C or warmer. “Border line moderate”. Hope this holds through at least January.

————————————————————————————————————————————————————-

A combination of a strong -AO/+PNA and much warmer than normal SSTA’s over the extreme Eastern Pacific up into the Gulf of AK is keeping a “very strong” upper ridge anchored along the west coast. Over the next week, there is hope that the upper jet over Eurasia and additional upper jet energy coming off Japan will combine and progress to the eastern pacific to give us a significant storm next week, Tuesday/Wednesday.

At the moment, the strong west coast upper ridge is keeping the weather warmer then normal. The Guidance indicates that a weak system will break through the upper ridge into California Wednesday Night/Thursday bringing some showers here and very light snowfall Thursday at elevations at and above 9,000 ft. The upper jet is about 100 knots and the main divergence portion of the upper jet is to our north. So we will get some showers and a dusting possibly up to an inch or so at and above 8500ft.

This weekend will be fair and a little warmer with the freezing level going back up to about 11,000ft by Sunday. It is in the extended range, next week, that holds promise for snowfall. All three global models the Dweebs looked at; IE the GEM, ECMWF, GFS and its extension the GFSX have a system that is able to break through the upper west coast ridge early next week. Over the next two days, the upper west coast ridge builds so far north that it morphs up into a closed blocking upper high that stretched from AK to the NW territories of Canada. This is in result of the weak under cutting upper jet into CA. In back of this system is more reinforcing short wave upper ridging that will provide for a fair weekend.

As the long wave Trough reloads NW of Hawaii from energy coming off Japan, upper jet energy is pushed eastward downstream through the west coast ridge again Tuesday and we get a moderate storm capable of a foot of snow or so. Now with that said , the mean ridge position will still be over us, but is in a weakened state. There will be some splitting going on, so no one at this time, including the models, have a true handle on who get the bulk of the snow. As a note, in a true El Nino year….the southern half of the state is usually favored in the split.

Now to look further out…..That energy that acts as a kicker NW of Hawaii, get squeezed toward CA later in the week as more and more short wave energy comes off Japan. In using the new Hi Res beta NCEP GFS T1534…… With the way the storm track is configured, the tempo will continue to pick up into that following weekend. Why? Not because the west coast ridge is gone. Rather, because heights have built up and formed a block from Just off the BC coast northward to the NW territories, then westward covering all of AK with the main positive upper height anomalies north of AK in the Arctic. The upper positive height anomaly then stretches westward along the Arctic circle then south over Eastern Siberia. The model suggest that upper Jet energy is forced south under this block at a latitude of about 45N when it is forced ESE into California that following weekend. More on this Later…….

1. Fridays High temp was 70 at the Ranger Station in town. That was the first 70 for that date breaking the previous record by 5 degrees in 2006.

2. Today Saturday is the last 70 ever recorded so late in the year. That occurred during the warm spell in 2006

3. The forecast high for today Saturday in Mammoth is 69. If we hit 70 by chance today, that would tie the warmest day so late in the Fall season.

4. A cool down will begin early next week as the upper high retrogrades west and cooler Canadian air slips south. The Models were showing a weak break through of the westerly’s next Thursday and a slight chance of some showers Thursday night and Friday.

5. No doubt the cooling trend will continue the next week with highs returning to more seasonal levels by Thursday and Friday. (Low 50s)

6. There is some suggestion this morning that a strengthening mid latitude upper jet may develop by the end of the 3rd week of November. This is just a suggestion at this time.

Saturday PM:

Weak under cutting is now expected later the new week with a slight chance of showers on Thursday. There is more evidence today with the ensembles, that a strengthening mid latitude upper jet will develop toward the 18th, 19 and 20th… However, The upper jet still is weakening at this point as it moves through the mean ridge position. Need more time to watch this……

The Dweebs acknowledge that the weather in California is way nicer then it needs to be this time of the year. And for those that are sweating it! No pun intended, it’s likely to continue more often than not the next couple of weeks…There will be record or near record highs for some stations reporting this weekend.

The big west coast ridge will be flattened at times for cooling and even the possibility of some showers over the next couple of week. However it is doubtful that we will get a meaningful storm before the 18th.

Are the Dweebs concerned at this time whether we’ll get any snow this year? Absolutely not… The Dweebs are concerned about the SSTA patterns along the west coast and up into the Gulf of AK. The Sea Surface temps along the west coast are running anomalies of +1C to +2.5C above normal, right up into the Gulf of AK.

“Upper Level highs” love Warmer than normal SSTs; (+SSTA’s), just like Continental Highs love the surface heat of the Desert SW. So we have a system in place that supports upper level ridging along the west coast, at least thermally. Contrary to some beliefs, anomalous warm water along the west coast does not have anything to do with a wet CA winter. The Warmer Water is often symptomatic of a Kelvin Wave that initiated it months before…or just a +PDO. Kelvin Waves can be associated with El Ninos or they may not be successful in it initiating it, in which case you just get warm water along the west coast, with often times a big upper ridge over the top of it.

Then you have to add in the Negative phase of the QBO which favors blocking over the Davis Straits and Greenland area. The east to west phase of the QBO also favors a -AO (Arctic Oscillation) which tends to suppress the Polar Vortex’s further south. The -AO is associated with higher surface pressure at the North Pole. So the combination of ridging from South along the west coast up into AK, plus a suppressed PV effecting the Great lakes South and East can make for warmer then normal Novembers into Winter. And lets also acknowledge the anomalous snow cover over Eurasia. That is another thermal anchor that effects the wave length across the pacific. All this together should keep the West Warm and Dry and the East Frigid. That is certainly what is probable over the next two weeks+. Will this be the winter? It was in 1976/77. The Wild Card is ENSO. We really do not know what it’s going to do. And it is too early to know for sure. We do not know for sure how strong it is going to be. NCEP just updated with a 58% chance of a weak El Nino. So odds are it will be a weak and to a lesser chance, a moderate El Nino. How much warmer does it need to be to be meaningful. Only .5C or about 1F warmer. That does not seem like that much, but it take a lot of energy to get there. It also needs to be throughout the entire Nino Basin…..Not just the central pacific. So we will have to wait a bit longer and see. It is worth noting that some of the rainiest years associated with El Nino had big west coast ridges where the westerlies under cut the west coast ridge. That is often associated with a teleconnection pattern called the (-TNH) IE the negative phase of the Tropical Northern Hemispheric Pattern.

From the CPC:

The TNH pattern reflects large-scale changes in both the location and eastward extent of the Pacific jet stream, and also in the strength and position of the climatological mean Hudson Bay Low (PV). Thus, the pattern significantly modulates the flow of marine air into North America, as well as the southward transport of cold Canadian air into the north-central United States.

The positive phase of the TNH pattern is associated with below-average surface temperatures throughout the western and central United States, and across central and eastern Canada. It is also associated with above-average precipitation across the central and eastern subtropical North Pacific, and below-average precipitation in the western United States and across Cuba, the Bahama Islands, and much of the central North Atlantic Ocean.

The negative phase of the TNH pattern is often observed during December and January when Pacific warm (ENSO) episode conditions are present (Barnston et al. 1991). One recent example of this is the 1994/95 winter season, when mature Pacific warm episode conditions and a strong negative phase of the TNH pattern were present. During this period, the mean Hudson Bay trough was much weaker than normal and shifted northeastward toward the Labrador Sea. Additionally, the Pacific jet stream was much stronger than normal and shifted southward to central California, well south of its climatological mean position in the Pacific Northwest. This flow pattern brought well above-normal temperatures to eastern North America and above-normal rainfall to the southwestern United States.

Longer Range:

The 32 day 51 member ensemble of the ECMWF monthly control initialized last Wednesday PM showed some retrogression of the upper ridge around the 18th of November. There was a system indicated that may bring some snow showers about the 19th or 20th. More significant retrogression was indicated about the 23rd with the beginnings of a west coast storm track Thanksgiving week. It is the type of storm track that would bring meaningful snowfall to the Sierra. Remember, this is an inter-seasonal outlook and subject to change……